1. Field of the Invention
The present invention relates to a multi-functional operating circuit which may be used for a microprocessor, an operating circuit for a digital signal processing LSI, another operating circuit dedicated to a computer field such as a workstation or a personal computer, an image processor, multi-media equipment or the like.
2. Description of the Related Art
In the field of processing digital data, in general, a microprocessor is widely used for various kinds of operations. Also in the field of image processing or communication, a digital signal processing is now allowed to be compressed or de-compressed. In the fields of processing digital data or a digital signal, an adding circuit or a multiplying circuit merely needs a fundamental operating circuit. As a result of progress of semiconductor technology, large-scale circuit integration is made possible.
The microprocessor known by the inventors of the present application includes operating circuits such an adder or a multiplier dispersively functioned in their own manners. That is, those operating circuits are not allowed to be freely arranged in response to an external instruction. Hence, in the case of designing (integrating) a multiplying circuit used for a microprocessor, no complex operating circuit is disallowed to be arranged. As such, though the operating circuit needs the fastest speed, it is difficult to prevent electric delay of a signal in designing the circuit, because there are provided operating units dispersively in light of functionality. The difficulty is an obstacle to high-density integration. The impossibility to arrange the operating units as an integrated operating circuit controlled in response to an external instruction results in lowering the flexibility of the known operating circuit in light of the architecture and additional operating functions.